U.S. patent application number 14/682125 was filed with the patent office on 2015-10-22 for d2d communications system and allocation method of resources and power using the same.
The applicant listed for this patent is SOONGSIL UNIVERSITY RESEARCH CONSORTIUM TECHNO- PARK. Invention is credited to Gil Mo KANG, Hyeon Min KIM, Oh-Soon SHIN.
Application Number | 20150305046 14/682125 |
Document ID | / |
Family ID | 54323191 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150305046 |
Kind Code |
A1 |
SHIN; Oh-Soon ; et
al. |
October 22, 2015 |
D2D COMMUNICATIONS SYSTEM AND ALLOCATION METHOD OF RESOURCES AND
POWER USING THE SAME
Abstract
A base station included in the D2D communication system: a
shared resource allocation unit configured to select a resource
block having highest performance in D2D communication from a
plurality of resource blocks occupied by a plurality of cellular
terminals and to set the shared resource block to be shared by a
corresponding D2D terminal; an exclusive resource allocation unit
configured to select at least one other D2D terminal with which to
share an exclusive resource block occupied by the corresponding D2D
terminal for the D2D communication and to set the exclusive
resource block to be shared by the at least one other D2D terminal;
and a power allocation unit configured to create a virtual resource
block by matching the shared resource block and the exclusive
resource block and to control powers allocated to the shared
resource block and the exclusive resource block included in the
virtual resource block.
Inventors: |
SHIN; Oh-Soon; (Seoul,
KR) ; KANG; Gil Mo; (Seoul, KR) ; KIM; Hyeon
Min; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SOONGSIL UNIVERSITY RESEARCH CONSORTIUM TECHNO- PARK |
Seoul |
|
KR |
|
|
Family ID: |
54323191 |
Appl. No.: |
14/682125 |
Filed: |
April 9, 2015 |
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 52/383 20130101;
H04W 72/06 20130101; H04W 52/241 20130101; H04W 72/08 20130101;
H04W 52/243 20130101; H04W 76/14 20180201 |
International
Class: |
H04W 72/08 20060101
H04W072/08; H04W 76/02 20060101 H04W076/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2014 |
KR |
10-2014-0046878 |
Mar 23, 2015 |
KR |
10-2015-0039991 |
Claims
1. A device-to-device (D2D) communication system D2D for sharing a
cellular resource, wherein a base station included in the D2D
communication system includes: a shared resource allocation unit
configured to select a resource block having highest performance in
D2D communication from a plurality of resource blocks occupied by a
plurality of cellular terminals and to set the shared resource
block to be shared by a corresponding D2D terminal; an exclusive
resource allocation unit configured to select at least one other
D2D terminal with which to share an exclusive resource block
occupied by the corresponding D2D terminal for the D2D
communication and to set the exclusive resource block to be shared
by the at least one other D2D terminal; and a power allocation unit
configured to create a virtual resource block by matching the
shared resource block and the exclusive resource block and to
control powers allocated to the shared resource block and the
exclusive resource block included in the virtual resource
block.
2. The D2D communication system of claim 1, wherein the shared
resource allocation unit selects a resource block having highest
D2D performance and sets the resource block as a shared resource
block according to the following equation: m * = arg max m log ( 1
+ n = 1 N h sh ( m , n ) d 2 d 2 .DELTA. ( m ) d 2 d n = 1 N h sh (
m , n ) c d 2 p sh ( m ) cue + N .sigma. 2 ) , ##EQU00021## where
m* represents the selected resource block, m represents the number
of cellular, h.sub.sh(m,n).sup.d2d represents a channel
corresponding to the shared resource block for the D2D
communication, .DELTA..sub.(m).sup.d2d represents a transmission
power threshold of the D2D terminal, h.sub.sh(m,n).sup.cd
represents a channel corresponding to the resource block between
the cellular terminal and the base station, p.sub.sh(m).sup.cue
represents a cellular communication power in the shared resource
block, and N represents the number of subcarriers, and .sigma.
represents a noise power.
3. The D2D communication system of claim 1, wherein the exclusive
resource allocation unit selects the D2D terminal with which to
share the exclusive resource block according to the following
equation: s * = arg max s .delta. s log ( 1 + n = 1 N h ex ( s , n
) d 2 d 2 p ex ( s ) d 2 d i = 1 i .noteq. s N s h ex ( i , n ) i 2
d 2 p ex ( i ) i 2 d + N .sigma. 2 ) , ##EQU00022## where s*
represents a selected D2D group, S represents a plurality of
detected candidate D2D terminal groups, h.sub.ex(s,n).sup.d2d
represents a channel corresponding to the exclusive resource block
for the D2D communication, p.sub.ex(s).sup.d2d represents a D2D
communication power in the exclusive resource block,
h.sub.ex(i,n).sup.i2d represents a channel corresponding to the D2D
terminal with which to share the exclusive resource block,
p.sub.ex(i).sup.i2d represents a communication power corresponding
to the D2D terminal with which to share the exclusive resource
block, N represents the number of subcarriers, and .sigma.
represents a noise power.
4. The D2D communication system of claim 1, wherein a condition of
n = 1 N p ex ( s , n ) + p sh ( s , n ) .ltoreq. P max , p [ ex ,
sh ] ( s , n ) .gtoreq. 0 and n = 1 N p sh ( s , n ) .ltoreq.
.DELTA. s ##EQU00023## is satisfied, the power allocation unit
calculates a maximum power of the set D2D group for the shared
resource block and the exclusive resource block included in the
virtual resource block according to the following equation:
Maximize s = 1 N s * n = 1 N log 2 ( 1 + h ex ( s , n ) d 2 d 2 p
ex ( s , n ) i = 1 i .noteq. s N s * h ex ( i , n ) i 2 d 2 p ex (
i , n ) + .sigma. 2 ) + log 2 ( 1 + h sh ( s , n ) d 2 d 2 p sh ( s
, n ) h sh ( s , n ) c d 2 p sh ( s , n ) cue + .sigma. 2 ) ,
##EQU00024## where .DELTA..sub.s represents the maximum
transmission power of a plurality of detected D2D groups,
h.sub.ex(s,n).sup.d2d represents a channel corresponding to the
exclusive resource block of the D2D communication terminal,
p.sub.ex(s,n) represents an initial power allocated to the
exclusive resource block, h.sub.ex(i,n).sup.i2d represents a
channel corresponding to an exclusive resource block of an i-th
candidate D2D communication terminal, p.sub.ex(i,n) represents
power allocated to the exclusive resource block of the i-th
candidate D2D communication terminal, h.sub.sh(s,n).sup.d2d
represents a channel corresponding to the shared resource block
between the corresponding D2D communication terminals,
p.sub.sh(s,n) represents an initial power allocated to the shared
resource block, h.sub.sh(s,n).sup.cd represents a channel
corresponding to the shared resource block between the cellular
terminal and the corresponding D2D communication terminal,
p.sub.sh(s,n).sup.cue represents a cellular power allocated to the
shared resource block, and .sigma. represents a noise power.
5. The D2D communication system of claim 4, wherein the power
allocation unit calculates power to be allocated to the shared
resource block included in the virtual resource block, and
allocates the calculated power according to the following equation:
P sh ( s , n ) * = ( 1 ln 2 1 .lamda. s + u s - h sh ( s , n ) c d
2 p sh ( s , n ) cue + .sigma. 2 h sh ( s , n ) d 2 d 2 ) + ,
##EQU00025## where P*.sub.sh(s,n) represents power to be allocated
to the shared resource block, P*.sub.ex(s,n) represents power to be
allocated to the exclusive resource block, .lamda..sub.s and
u.sub.s represent lagrange multipliers, h.sub.sh(s,n).sup.cd
represents a channel corresponding to the shared resource block
between the cellular terminal and the corresponding D2D
communication terminal, p.sub.sh(s,n).sup.cue represents a cellular
power allocated to the shared resource block, h.sub.sh(s,n).sup.d2d
represents a channel corresponding to the shared resource block of
the corresponding D2D communication terminal, .sigma. represents a
noise power, and (x).sup.+.ident.min(0,x).
6. The D2D communication system of claim 4, wherein the power
allocation unit calculates power to be allocated to the exclusive
resource block included in the virtual resource block, and
allocates the calculated power according to the following equation:
P ex ( s , n ) * = ( 1 ln 2 1 i = 1 i .noteq. s N s * C ex ( i , n
) h ex ( i , n ) i 2 d 2 + .lamda. s - i = 1 i .noteq. s N s * h ex
( i , n ) i 2 d 2 p ex ( i ) i 2 d + .sigma. 2 h ex ( s , n ) d 2 d
2 ) + , ##EQU00026## where P*.sub.ex(s,n) represents power
allocated to the exclusive resource block, C.sub.ex(i,n) represents
.differential. R ( i , n ) .differential. I d ( i , n ) ,
##EQU00027## h.sub.ex(i,n).sup.i2d represents a channel
corresponding to an exclusive resource block of an i-th candidate
D2D communication terminal, p.sub.ex(i).sup.i2d represents power of
the i-th candidate D2D terminal in the exclusive resource block,
h.sub.ex(i,n).sup.d2d represents a channel corresponding to the
exclusive resource block of the corresponding D2D communication
terminal, and (x).sup.+.ident.min(0,x).
7. A method of allocating resources and power by a base station
included in a D2D communication system for sharing a cellular
resource, comprising: selecting a resource block having highest
performance in D2D communication from a plurality of resource
blocks and setting the resource block as a shared resource block to
be shared by a corresponding D2D terminal; selecting at least one
other D2D terminal with which to share an exclusive resource block
occupied by the corresponding D2D terminal for the D2D
communication and setting the exclusive resource block to be shared
by the at least one other D2D terminal; and creating a virtual
resource block by matching the shared resource block and the
exclusive resource block and then controlling powers allocated to
the exclusive resource block included in the virtual resource
block.
8. The method of claim 7, wherein the setting of the resource block
as the shared resource block to be shared by the corresponding D2D
terminal sets the resource block having highest D2D performance as
the shared resource block according to the following equation: m *
= arg max m log ( 1 + n = 1 N h sh ( m , n ) d 2 d 2 .DELTA. ( m )
d 2 d n = 1 N h sh ( m , n ) c d 2 p sh ( m ) cue + N .sigma. 2 ) ,
##EQU00028## where m* represents the selected resource block, m
represents the number of cellular terminals, h.sub.sh(m,n).sup.d2d
represents a channel corresponding to the shared resource block for
the D2D communication, .DELTA..sub.(m).sup.d2d represents a
transmission power threshold of the D2D terminal,
h.sub.sh(m,n).sup.cd represents a channel corresponding to the
resource block between the cellular terminal and the base station,
p.sub.sh(m).sup.cue represents a cellular communication power in
the shared resource block, N represents the number of subcarriers,
and .sigma. represents a noise power.
9. The method of claim 7, wherein the setting of the exclusive
resource block to be shared by the at least one other D2D terminal
and the corresponding D2D terminal selects the D2D terminal with
which to share the exclusive resource block according to the
following equation: s * = arg max s .delta. s log ( 1 + n = 1 N h
ex ( s , n ) d 2 d 2 p ex ( s ) d 2 d i = 1 i .noteq. s N s h ex (
i , n ) i 2 d 2 p ex ( i ) i 2 d + N .sigma. 2 ) , ##EQU00029##
where s* represents a selected D2D group, S represents a plurality
of detected candidate D2D terminal groups, h.sub.ex(s,n).sup.d2d
represents a channel corresponding to the exclusive resource block
for the D2D communication, p.sub.ex(s).sup.d2d represents a D2D
communication power in the exclusive resource block,
h.sub.ex(i,n).sup.i2d represents a channel corresponding to the D2D
terminal with which to share the exclusive resource block,
p.sub.ex(i).sup.i2d represents a communication power corresponding
to the D2D terminal with which to share the exclusive resource
block, N represents the number of subcarriers, and .sigma.
represents a noise power.
10. The method of claim 7, wherein, when a condition of n = 1 N p
ex ( s , n ) + p sh ( s , n ) .ltoreq. P max , p [ ex , sh ] ( s ,
n ) .gtoreq. 0 and n = 1 N p sh ( s , n ) .ltoreq. .DELTA. s
##EQU00030## is satisfied, the controlling of the powers allocated
to the shared resource block and the exclusive resource block
calculates power of the set D2D group for the shared resource block
and the exclusive resource block included in the virtual resource
block according to the following equation: Maximize s = 1 N s * n =
1 N log 2 ( 1 + h ex ( s , n ) d 2 d 2 p ex ( s , n ) i = 1 i
.noteq. s N s * h ex ( i , n ) i 2 d 2 p ex ( i , n ) + .sigma. 2 )
+ log 2 ( 1 + h sh ( s , n ) d 2 d 2 p sh ( s , n ) h sh ( s , n )
c d 2 p sh ( s , n ) cue + .sigma. 2 ) , ##EQU00031## where
.DELTA..sub.s represents a maximum transmission power of a
plurality of detected D2D groups, h.sub.ex(s,n).sup.d2d represents
a channel corresponding to the exclusive resource block of the D2D
communication terminal, p.sub.ex(s,n) represents an initial power
allocated to the exclusive resource block, h.sub.ex(i,n).sup.i2d
represents a channel corresponding to an exclusive resource block
of an i-th candidate D2D communication terminal, p.sub.ex(i,n)
represents power allocated to an exclusive resource block of the
i-th candidate D2D communication terminal, h.sub.sh(s,n).sup.d2d
represents a channel corresponding to the shared resource block
between the corresponding D2D communication terminals,
p.sub.sh(s,n) represents an initial power allocated to the shared
resource block, h.sub.sh(s,n).sup.cd represents a channel
corresponding to the shared resource block between the cellular
terminal and the corresponding D2D communication terminal,
p.sub.sh(s,n).sup.cue represents a cellular power allocated to the
shared resource block, and .sigma. represents a noise power.
11. The method of claim 10, wherein the controlling of the power
allocated to the shared resource block calculates the power to be
allocated to the shared resource block included in the virtual
resource block, and allocates the calculated power according to the
following equation: P sh ( s , n ) * = ( 1 ln 2 1 .lamda. s + u s -
h sh ( s , n ) c d 2 p sh ( s , n ) cue + .sigma. 2 h sh ( s , n )
d 2 d 2 ) + , ##EQU00032## where P*.sub.sh(s,n) represents power to
be allocated to the shared resource block, P*.sub.ex(s,n)
represents power to be allocated to the exclusive resource block,
.lamda..sub.s and u.sub.s represent lagrange multipliers,
h.sub.sh(s,n).sup.cd represents a channel corresponding to the
shared resource block between the cellular terminal and the
corresponding D2D communication terminal, p.sub.sh(s,n).sup.cue
represents a cellular power allocated to the shared resource block,
h.sub.sh(s,n).sup.d2d represents a channel corresponding to the
shared resource block of the corresponding D2D communication
terminal, .sigma. represents a noise power, and
(x).sup.+.ident.min(0,x).
12. The method of claim 10, wherein the controlling of the power
allocated to the exclusive resource block calculates power to be
allocated to the exclusive resource block included in the virtual
resource block, and allocates the calculated power according to the
following equation: P ex ( s , n ) * = ( 1 ln 2 1 i = 1 i .noteq. s
N s * C ex ( i , n ) h ex ( i , n ) i 2 d 2 + .lamda. s - i = 1 i
.noteq. s N s * h ex ( i , n ) i 2 d 2 p ex ( i ) i 2 d + .sigma. 2
h ex ( s , n ) d 2 d 2 ) + , ##EQU00033## where P*.sub.ex(s,n)
represents power allocated to the exclusive resource block,
C.sub.ex(i,n) represents .differential. R ( i , n ) .differential.
I d ( i , n ) , ##EQU00034## h.sub.ex(i,n).sup.i2d represents a
channel corresponding to an exclusive resource block of an i-th
candidate D2D communication terminal, p.sub.ex(i).sup.i2d
represents power of the i-th candidate D2D terminal in the
exclusive resource block, h.sub.ex(s,n).sup.d2d represents a
channel corresponding to the exclusive resource block of the
corresponding D2D communication terminal, and
(x).sup.+.ident.min(0,x).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 10-2014-0046878 filed on Apr. 18, 2014 and Korean
Patent Application No. 10-2015-0039991 filed on Mar. 23, 2015, in
the Korean Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] (a) Field of the Invention
[0003] The present invention relates to a device-to-device (D2D)
communication system and a method for allocating resources and
power using the same, and more particularly, to a D2D communication
system and a method for allocating D2D resources and power to
maximize spectral efficiency using the same in a cellular system
for supporting D2D communication.
[0004] (b) Description of the Related Art
[0005] Recently, as various services using a wireless mobile
communication system are provided, data traffic has drastically
increased, and a device-to-device (D2D) communication in a cellular
system is under research and development (R&D) and
standardization to solve such a problem.
[0006] The D2D communication allows adjacent terminals to directly
communicate each other without passing through infrastructure such
as a base station and the like, thereby enabling a new service
based on proximity and improving spectral efficiency of the
cellular system at the same time.
[0007] Therefore, a D2D link needs to share an existing cellular
frequency resource with a cellular link so as to improve spectral
efficiency.
[0008] However, while the D2D link share the existing cellular
frequency resource with the cellular link to improve the spectral
efficiency, interference there between may occur.
[0009] As such, as a research is being carried out to allow the D2D
communication and the cellular communication to use the same
communication band, appropriate resource allocation and power
distribution of the D2D communication has become a critical issue
to reduce mutual interference between the D2D communication and the
cellular communication.
[0010] In the most typical approach to allocating resources in the
cellular link and the D2D link, the base station collects
information about channel statuses of respective links and mutually
interfered links, and then performs resource allocation based on
the collected information.
[0011] Such an approach has a merit of correctly measuring
influence of interference, but it is not desirable because an
optimization issue such as increased complexity in measuring and
collecting channel information, signaling overhead increase, and a
complex resource allocation algorithm should be addressed.
[0012] In addition, in the case of a time-varying channel that
varies at a very high speed, performance degradation may be a
serious problem since it is difficult to obtain correct channel
information.
[0013] Another aspect that is not considered in conventional
resource allocation schemes is to determine which resources are
effective to share with.
[0014] For example, it may be difficult to share a D2D link of a
cellular user's resource near a cell edge because of severe
interference.
[0015] Accordingly, the resource allocation algorithm needs to be
designed such that it preferentially shares a resource with less
interference.
[0016] Further, the existing cellular communication and the D2D
communication have been considered as separate systems with respect
to each other, so resource and power allocations for the cellular
communication and the D2D communication are independently
performed.
[0017] The background art of the present invention is disclosed in
the Korean Patent Laid-Open Publication No. 2008-0028347 (laid-open
on Mar. 31, 2008).
SUMMARY OF THE INVENTION
[0018] The present invention has been made in an effort to provide
a device-to-device (D2D) communication system for allocating D2D
resources and power to maximize spectral efficiency and a method
using the same in a cellular system for supporting the D2D
communication.
[0019] An exemplary embodiment of the present invention provides a
D2D communication system for sharing a cellular resource. A base
station included in the D2D communication system includes: a shared
resource allocation unit configured to select a resource block
having highest performance in D2D communication from a plurality of
resource blocks occupied by a plurality of cellular terminals and
to set the shared resource block to be shared by a corresponding
D2D terminal; an exclusive resource allocation unit configured to
select at least one other D2D terminal with which to share an
exclusive resource block occupied by the corresponding D2D terminal
for the D2D communication and to set the exclusive resource block
to be shared by the at least one other D2D terminal; and a power
allocation unit configured to create a virtual resource block by
matching the shared resource block and the exclusive resource block
and to control powers allocated to the shared resource block and
the exclusive resource block included in the virtual resource
block.
[0020] The shared resource allocation unit may select a resource
block having highest D2D performance and set the resource block as
a shared resource block according to the following equation:
m * = arg max m log ( 1 + n = 1 N h sh ( m , n ) d 2 d 2 .DELTA. (
m ) d 2 d n = 1 N h sh ( m , n ) cd 2 P sh ( m ) cue + N.sigma. 2 )
, ##EQU00001##
where m* represents the selected resource block, m represents the
number of cellular, h.sub.sh(m,n).sup.d2d represents a channel
corresponding to the shared resource block for the D2D
communication, .DELTA..sub.(m).sup.d2d represents a transmission
power threshold of the D2D terminal, h.sub.sh(m,n).sup.cd
represents a channel corresponding to the resource block between
the cellular terminal and the base station, p.sub.sh(m).sup.cue
represents a cellular communication power in the shared resource
block, and N represents the number of subcarriers, and .sigma.
represents a noise power.
[0021] The exclusive resource allocation unit may select the D2D
terminal with which to share the exclusive resource block according
to the following equation:
s * = arg max s .delta. s log ( 1 + n = 1 N h ex ( s , n ) d 2 d 2
P ex ( s ) d 2 d i = 1 i .noteq. s N s h ex ( i , n ) i 2 d 2 P ex
( i ) i 2 d + N .sigma. 2 ) , ##EQU00002##
where s* represents a selected D2D group, S represents a plurality
of detected candidate D2D terminal groups, h.sub.ex(s,n).sup.d2d
represents a channel corresponding to the exclusive resource block
for the D2D communication, p.sub.ex(s).sup.d2d represents a D2D
communication power in the exclusive resource block,
h.sub.ex(i,n).sup.i2d represents a channel corresponding to the D2D
terminal with which to share the exclusive resource block,
p.sub.ex(i).sup.i2d represents a communication power corresponding
to the D2D terminal with which to share the exclusive resource
block, N represents the number of subcarriers, and .sigma. a noise
power.
[0022] Wherein a condition of
n = 1 N p ex ( s , n ) + p sh ( s , n ) .ltoreq. P max , p ( ex ,
sh ) ( s , n ) .gtoreq. 0 and n = 1 N p sh ( s , n ) .ltoreq.
.DELTA. s ##EQU00003##
is satisfied, the power allocation unit may calculate a maximum
power of the set D2D group for the shared resource block and the
exclusive resource block included in the virtual resource block
according to the following equation:
Maximize s = 1 N s n = 1 N log 2 ( 1 + h ex ( s , n ) d 2 d 2 P ex
( s , n ) i = 1 i .noteq. s N s h ex ( i , n ) i 2 d 2 P ex ( i , n
) + .sigma. 2 ) + log 2 ( 1 + h sh ( s , n ) d 2 d 2 P sh ( s , n )
h sh ( s , n ) c d 2 P sh ( s , n ) cue + .sigma. 2 ) ,
##EQU00004##
where .DELTA..sub.s represents the maximum transmission power of a
plurality of detected D2D groups, h.sub.ex(s,n).sup.d2d represents
a channel corresponding to the exclusive resource block of the D2D
communication terminal, p.sub.ex(s,n) represents an initial power
allocated to the exclusive resource block, h.sub.ex(i,n).sup.i2d
represents a channel corresponding to an exclusive resource block
of an i-th candidate D2D communication terminal, p.sub.ex(i,n)
represents power allocated to the exclusive resource block of the
i-th candidate D2D communication terminal, h.sub.sh(s,n).sup.d2d
represents a channel corresponding to the shared resource block
between the corresponding D2D communication terminals,
p.sub.sh(s,n) represents an initial power allocated to the shared
resource block, h.sub.sh(s,n).sup.cd represents a channel
corresponding to the shared resource block between the cellular
terminal and the corresponding D2D communication terminal,
p.sub.sh(s,n).sup.cue represents a cellular power allocated to the
shared resource block, and .sigma. represents a noise power.
[0023] The power allocation unit may calculate power to be
allocated to the shared resource block included in the virtual
resource block and allocate the calculated power according to the
following equation:
P sh ( s , n ) * = ( 1 ln 2 1 .lamda. s + .mu. s - h sh ( s , n )
cd 2 p sh ( s , n ) cue + .sigma. 2 h sh ( s , n ) d 2 d 2 ) + ,
##EQU00005##
where P*.sub.sh(s,n) represents power to be allocated to the shared
resource block, P*.sub.ex(s,n) represents power to be allocated to
the exclusive resource block, and represent lagrange multipliers,
h.sub.sh(s,n).sup.cd represents a channel corresponding to the
shared resource block between the cellular terminal and the
corresponding D2D communication terminal, p.sub.sh(s,n).sup.cue
represents a cellular power allocated to the shared resource block,
h.sub.sh(s,n).sup.d2d represents a channel corresponding to the
shared resource block of the corresponding D2D communication
terminal, .sigma. represents a noise power, and
(x).sup.+.ident.min(0,x).
[0024] The power allocation unit may calculate power to be
allocated to the exclusive resource block included in the virtual
resource block and allocate the calculated power according to the
following equation:
P ex ( s , n ) * = ( 1 ln 2 1 i = 1 i .noteq. s N s * C ex ( i , n
) h ex ( i , n ) i 2 d 2 + .lamda. s - i = 1 i .noteq. s N s * h ex
( i , n ) i 2 d 2 p ex ( i ) i 2 d + .sigma. 2 h ex ( s , n ) d 2 d
2 ) + , ##EQU00006##
where P*.sub.ex(s,n) represents power allocated to the exclusive
resource block, C.sub.ex(i,n) represents
.differential. R ( i , n ) .differential. I d ( i , n ) ,
##EQU00007##
h.sub.ex(i,n).sup.i2d represents a channel corresponding to an
exclusive resource block of an i-th candidate D2D communication
terminal, p.sub.ex(i).sup.i2d represents power of the i-th
candidate D2D terminal in the exclusive resource block,
h.sub.ex(s,n).sup.d2d represents a channel corresponding to the
exclusive resource block of the corresponding D2D communication
terminal, and (x).sup.+.ident.min(0,x).
[0025] According to another exemplary embodiment of the present
invention, a method of allocating resources and power by a base
station included in a D2D communication system for sharing a
cellular resource, includes: selecting a resource block having
highest performance in D2D communication from a plurality of
resource blocks and setting the resource block as a shared resource
block to be shared by a corresponding D2D terminal; selecting at
least one other D2D terminal with which to share an exclusive
resource block occupied by the corresponding D2D terminal for the
D2D communication and setting the exclusive resource block to be
shared by the at least one other D2D terminal; and creating a
virtual resource block by matching the shared resource block and
the exclusive resource block and then controlling powers allocated
to the exclusive resource block included in the virtual resource
block.
[0026] According to the present invention, in the D2D system using
the cellular resources, spectral efficiency of the D2D system can
be improved through the resource allocation for sharing the
resource of the cellular user as well as the exclusive resource
allocation for the D2D user.
[0027] In addition, when sharing the cellular resource, the D2D
transmission power is limited to ensure performance of the cellular
user, a plurality of D2D users form a group for the exclusive
resource and reuse the same resource spatially, thereby improving
spectrum efficiency and performance of the entire cells.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0029] FIG. 1 is a drawing for describing an interference scenario
in a downlink and an uplink according to an exemplary embodiment of
the present invention.
[0030] FIG. 2 is a schematic diagram of a base station included in
a device-to-device (D2D) communication system according to the
exemplary embodiment of the present invention.
[0031] FIG. 3 is a flowchart for illustrating a method for
allocating resources and power according to an exemplary embodiment
of the present invention.
[0032] FIG. 4 is a drawing for illustrating a virtual resource
block for D2D communication according to the exemplary embodiment
of the present invention.
[0033] FIG. 5 is a drawing for illustrating spectral efficiency
associated with D2D transmission powers according to the exemplary
embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] The present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown.
[0035] As those skilled in the art would realize, the described
embodiments may be modified in various different ways, all without
departing from the spirit or scope of the present invention.
[0036] Accordingly, the drawings and description are to be regarded
as illustrative in nature and not restrictive, and like reference
numerals designate like elements throughout the specification.
[0037] Throughout the specification, unless explicitly described to
the contrary, the word "comprise" and variations such as
"comprises" or "comprising" will be understood to imply the
inclusion of stated elements but not the exclusion of any other
elements.
[0038] The present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown.
[0039] FIG. 1 is a drawing for describing an interference scenario
in a downlink and an uplink according to an exemplary embodiment of
the present invention.
[0040] A base station BS of a wireless mobile communication system
may be a base station of a device-to-device (D2D) terminal D-UE
(Direct-UE) for enabling D2D communication with a user terminal UE
or a small cell and a pico cell.
[0041] A method of the user terminal UE communicating via the base
station BS is represented by a cellular communication, and a method
of the user terminal UE directly communicating with the D2D
terminal D-UE without via the base station BS is represent by a D2D
communication.
[0042] The user terminal UE receives a signal from the base station
and the D2D terminal through the downlink.
[0043] In this case, interference from the base station, in
addition to interference from the D2D terminal to other user
terminals using a corresponding resource, exists in the user
terminal UE.
[0044] The user terminal UE transmits a signal to the base station
and the D2D terminal through the uplink.
[0045] In this case, there are interference received by the base
station and interference coming from other user terminal to be
received by the D2D terminal.
[0046] Among the interferences in the respective links, a user
terminal may use a channel corresponding to deep shadowing or deep
fading to exchange channel status information (CSI) with the base
station, thereby reducing the interference in the downlink from the
base station.
[0047] In addition, performance degradation due to the interference
can be easily overcome in the downlink since transmission power is
greater in the downlink than in the uplink, whereas in the uplink,
maximum transmission power of the user terminal is small and thus
transmission power is greatly limited by the interference that the
base station receives.
[0048] Accordingly, in the exemplary embodiment of the present
invention, resource and power allocations are proposed to achieve a
maximum data rate of the uplink in the overall D2D communication
system.
[0049] Next, referring to FIG. 2, a base station included in a D2D
communication system according to the exemplary embodiment of the
present invention will be described.
[0050] FIG. 2 is a schematic diagram of the base station included
in the D2D communication system according to the exemplary
embodiment of the present invention.
[0051] The base station 100 included in the D2D communication
system includes a shared resource allocation unit 110, an exclusive
resource allocation unit 120, and a power allocation unit 130.
[0052] The shared resource allocation unit 110 selects a resource
block having highest performance in the D2D communication from a
plurality of resource blocks occupied by a plurality of cellular
terminals, and sets it as a shared resource block to be shared by
the corresponding D2D terminal.
[0053] The shared resource allocation unit 110 selects the most
efficient shared resource block for the corresponding D2D terminal
using an equation of a transmission power threshold of the D2D
terminal through an average signal-to-noise ratio (SNR) of a
cellular user.
[0054] The exclusive resource allocation unit 120 allows the D2D
communication terminal to exclusively use some of cellular
resources.
[0055] Further, for the D2D communication, the exclusive resource
allocation unit 120 selects and sets up an optimal D2D terminal or
a D2D communication group such that the exclusive resource block
occupied by the corresponding D2D communication terminal can be
opportunistically reused by at least one other D2D communication
terminal.
[0056] The power allocation unit 130 creates a virtual resource
block by matching the shared resource block and the exclusive
resource block that are selected by the shared resource allocation
unit 110 and the exclusive resource allocation unit 120, and
controls powers allocated to the shared resource block and the
exclusive resource block that are included in the virtual resource
block.
[0057] The power allocation unit 130 collects power of each of the
D2D terminals in real-time as an initial value, and calculates and
controls power of each of the resource blocks.
[0058] In this case, in response to the power values and the
interferences collected in real-time, the power allocation unit 130
controls the power of the virtual resource block of each D2D
terminal such that an overall performance of the D2D communication
is optimal.
[0059] That is, while maintaining a total amount of power, the
power allocation unit 130 adjusts and controls the powers of the
shared resource block and the exclusive resource block.
[0060] A method for allocating resources and power will now be
described with reference to FIGS. 3 and 4.
[0061] FIG. 3 is a flowchart for illustrating a method for
allocating resources and power according to an exemplary embodiment
of the present invention, and FIG. 4 is a drawing for illustrating
a virtual resource block for D2D communication according to the
exemplary embodiment of the present invention.
[0062] First, a base station 100 included in a D2D communication
system selects a resource block having highest performance in a D2D
communication from a plurality of resource blocks occupied by a
plurality of cellular terminals, and sets it as a shared resource
block to be shared by a corresponding D2D terminal (S310).
[0063] Since the base station 100 should guarantee quality of
service (QoS) of a user, an average SNR of cellular users is used
to calculate a transmission power threshold of the D2D terminal,
and a D2D terminal may be selected according to Equation 1.
[0064] The base station 100 calculates to select the resource block
having the highest performance for the corresponding D2D terminal
from the plurality of resource blocks using the following Equation
1.
m * = arg max log m ( 1 + n = 1 N h sh ( m , n ) d 2 d 2 .DELTA. (
m ) d 2 d n = 1 N h sh ( m , n ) cd 2 p sh ( m ) cue + N .sigma. 2
) [ Equation 1 ] ##EQU00008##
[0065] Herein, m* represents the selected resource block, m
represents the number of cellular, h.sub.sh(m,n).sup.d2d represents
a channel corresponding to a shared resource block for the D2D
communication, .DELTA..sub.(m).sup.d2d represents a transmission
power threshold of the D2D terminal, h.sub.sh(m,n).sup.cd
represents a channel corresponding to the resource block between
the cellular terminal and the base station, p.sub.sh(m).sup.cue
represents a cellular communication power in the shared resource
block, N represents the number of subcarriers, and .sigma.
represents a noise power.
[0066] Next, the base station 100 selects at least one other D2D
terminal with which to share the exclusive resource block occupied
by the corresponding D2D terminal for the D2D communication, and
sets it to be shared by the corresponding D2D terminal (S320).
[0067] The base station 100 selects the at least one other D2D
terminal with which to share the exclusive resource block occupied
by the corresponding D2D terminal according to the following
Equation 2.
s * = arg max s .delta. s log ( 1 + n = 1 N h ex ( s , n ) d 2 d 2
p ex ( s ) d 2 d i = 1 i .noteq. s N s * h ex ( i , n ) i 2 d 2 p
ex ( i ) i 2 d + N .sigma. 2 ) [ Equation 2 ] ##EQU00009##
[0068] Herein, s* represents a selected D2D group, S represents a
plurality of candidate D2D terminal groups, h.sub.ex(s,n).sup.d2d
represents a channel corresponding to the exclusive resource block
for the D2D communication, represents a D2D communication power in
the exclusive resource block, represents a channel corresponding to
the D2D terminal with which to share the exclusive resource block,
p.sub.ex(i).sup.i2d represents a communication power corresponding
to the D2D terminal with which to share the exclusive resource
block, N represents the number of subcarriers, and .sigma.
represents a noise power.
[0069] Finally, the base station 100 creates a virtual resource
block by matching the shared resource block and the exclusive
resource block, and then controls powers allocated to the shared
resource block and the exclusive resource block that are included
in the virtual resource block (S330).
[0070] FIG. 4 illustrates a D2D communications resource block, that
is, the virtual resource block in which the shared resource block
and the exclusive resource block are matched.
[0071] That is, in the exemplary embodiment of the present
invention, FIG. 4 illustrates the virtual resource block in which
the exclusive resource for D2D set (EX) for the D2D communication
and the shared resource with cellular (SH) used by both the
cellular communication and the D2D communication are matched.
[0072] As such, the respective resource blocks in the virtual
resource block are influenced by different interferences.
[0073] That is, there are interference from the other D2D
communication terminal communicating in the exclusive resource EX
(interference from D2D set) and interference from the base station
for cellular communication in the shared resource SH (interference
from CUE).
[0074] In addition, the exclusive resource EX and the shared
resource SH include the number of subcarriers (N) that is used to
modulate a carrier.
[0075] As such, the base station 100 performs optimal power
allocation for each of the resource blocks included in the virtual
resource block so as to achieve a maximum data rate of an overall
D2D communication system.
[0076] If the shared resource block and the exclusive resource
block included in the virtual resource block satisfy a condition
of
n = 1 N p ex ( s , n ) + p sh ( s , n ) .ltoreq. P max , p ( ex ,
sh ) ( s , n ) .gtoreq. 0 and n = 1 N p sh ( s , n ) .ltoreq.
.DELTA. s , ##EQU00010##
the base station 100 may calculate a maximum power of the
predetermined D2D group set by the following Equation 3.
Maximize s = 1 N s * n = 1 N log 2 ( 1 + h ex ( s , n ) d 2 d 2 p
ex ( s , n ) i = 1 i .noteq. s N s * h ex ( i , n ) d 2 d 2 p ex (
i , n ) + .sigma. 2 ) + log 2 ( 1 + h sh ( s , n ) d 2 d 2 p sh ( s
, n ) h sh ( s , n ) cd 2 p sh ( s , n ) cue + .sigma. 2 ) [
Equation 3 ] ##EQU00011##
[0077] Herein, .DELTA..sub.s represents a maximum transmission
power of a plurality of detected D2D groups, h.sub.ex(s,n).sup.d2d
represents a channel corresponding to the exclusive resource block
of the D2D communication terminal, p.sub.ex(s,n) represents an
initial power allocated to the exclusive resource block,
h.sub.ex(i,n).sup.i2d represents a channel corresponding to an
exclusive resource block of an i-th candidate D2D communication
terminal, p.sub.ex(i,n) represents power allocated to an exclusive
resource block of an i-th candidate D2D communication terminal,
h.sub.sh(s,n).sup.d2d represents a channel corresponding to the
shared resource block between the corresponding D2D communication
terminals, p.sub.sh(s,n) represents an initial power allocated to
the shared resource block, h.sub.sh(s,n).sup.cd represents a
channel corresponding to the shared resource block between the
cellular terminal and the corresponding D2D communication terminal,
p.sub.sh(s,n).sup.cue represents a cellular power allocated to the
shared resource block, and .sigma. represents a noise power.
[0078] The base station 100 calculates Equation 3 using a
lagrangian function and a karush-kuhn-tucker (KKT) condition like
Equation 4.
L ( p ex , p sh , .lamda. s , u s ) = s = 1 n = 1 R ( p ex , p sh )
- .lamda. s ( p ex ( s , n ) d 2 d + p sh ( s , n ) d 2 d ) - u s p
sh ( s , n ) d 2 d + s = 1 N s * .lamda. s P max + s = 1 N s * u s
.DELTA. s .differential. L .differential. p ex = .differential. R (
p ex , p sh ) .differential. p ex + .differential. z = 1 z .noteq.
s N s * R ( p ex , p sh ) .differential. p ex - .lamda. s
.differential. L .differential. p sh = .differential. R ( p ex , p
sh ) .differential. p sh - ( .lamda. s + u s ) = 0 , .lamda. s ( n
= 1 N ( p ex ( s , n ) + p sh ( s , n ) ) - P max ) = 0. u s ( n =
1 N p sh ( s , n ) - .DELTA. s ) = 0 [ Equation 4 ]
##EQU00012##
[0079] Next, the base station 100 calculates power to be allocated
to the shared resource block included in the virtual resource block
using Equation 5 from the karush-kuhn-tucker (KKT) condition like
Equation 4.
P sh ( s , n ) * = ( 1 ln 2 1 .lamda. s + u s - h sh ( s , n ) cd 2
p sh ( s , n ) cue + .sigma. 2 h sh ( s , n ) d 2 d 2 ) + [
Equation 5 ] ##EQU00013##
[0080] Herein, P*.sub.sh(s,n) represents power to be allocated to
the shared resource block, P*.sub.ex(s,n) represents power to be
allocated to the exclusive resource block, .lamda..sub.s and
u.sub.s represent lagrange multipliers, h.sub.sh(s,n).sup.cd
represents a channel corresponding to the shared resource block
between the cellular terminal and the corresponding D2D
communication terminal, p.sub.sh(s,n).sup.cue represents a cellular
power allocated to the shared resource block, h.sub.sh(s,n).sup.d2d
represents a channel corresponding to the shared resource block of
the corresponding D2D communication terminal, .sigma. represents a
noise power, and (x).sup.+.ident.min(0,x).
[0081] In addition, the base station 100 calculates power to be
allocated to the exclusive resource block included in the virtual
resource block using Equation 6 from the karush-kuhn-tucker (KKT)
condition like Equation 4.
P ex ( s , n ) * = ( 1 ln 2 1 i = 1 i .noteq. s N s * C ex ( i , n
) h ex ( i , n ) i 2 d 2 + .lamda. s - i = 1 i .noteq. s N s * h ex
( i , n ) i 2 d 2 + p ex ( i ) i 2 d + .sigma. 2 h ex ( s , n ) d 2
d 2 ) + [ Equation 6 ] ##EQU00014##
[0082] Herein, P*.sub.ex(s,n) represents power allocated to the
exclusive resource block, C.sub.ex(i,n) represents
.differential. R ( i , n ) .differential. I d ( i , n ) ,
##EQU00015##
h.sub.ex(i,n).sup.i2d represents a channel corresponding to an
exclusive resource block of an i-th candidate D2D communication
terminal, p.sub.ex(i).sup.i2d represents power of the i-th
candidate D2D terminal in the exclusive resource block,
h.sub.ex(s,n).sup.d2d represents a channel corresponding to the
exclusive resource block of the corresponding D2D communication
terminal, and (x).sup.+.ident.min(0,x).
[0083] In this case, C.sub.ex(i,n) represents a performance sum of
the group differentiated by power as in
i = 1 i .noteq. s N s * C ex ( i , n ) h ex ( i , n ) i 2 d 2 =
.differential. z = 1 z .noteq. s N s * R ( p ex , p sh )
.differential. p ex , ##EQU00016##
and it may be calculated according to the following Equation 7.
.differential. R ( i , n ) .differential. I d ( i , n ) = - 1 ln 2
h ex ( i , n ) D 2 D 2 p ex ( i , n ) ( .sigma. 2 + I d ( i , n ) )
2 + ( .sigma. 2 + I d ( i , n ) ) h ex ( i , n ) D 2 D 2 p ex ( i ,
n ) .ident. - C ex ( i , n ) [ Equation 7 ] ##EQU00017##
[0084] Herein, .sigma. represents a noise power, i.e., interference
between D2D groups using resources such as I.sub.d.
[0085] The base station 100 may calculate the power allocated to
the exclusive resource block by applying the KKT condition of
Equation 4 and
i = 1 i .noteq. s N s * C ex ( i , n ) h ex ( i , n ) i 2 d 2 =
.differential. z = 1 z .noteq. s N s * R ( p ex , p sh )
.differential. p ex ##EQU00018##
to Equation 6.
[0086] As described above, using Equation 5 and Equation 6, the
base station 100 calculates the powers to be allocated to the
shared resource block and the exclusive resource block that are
included in the virtual resource block, and accordingly controls
power.
[0087] An algorithm proposed according to the exemplary embodiment
of the present invention is shown in the following Table 1.
TABLE-US-00001 TABLE 1 Shared resource allocation 1 .ltoreq. m
.ltoreq. M find m* using [Equation 1] D2D group formation &
initial power setting 1 .ltoreq. s .ltoreq. N.sub.s find p 0 using
y s = 1 N .alpha. 2 n = 1 N | h ex ( s , n ) d 2 d | 2 p ex ( s , n
) d 2 d ##EQU00019## find s* using [Equation 2] Optimal D2D power
allocation through [Equation 5] and [Equation 6] with m*, s*,
p.sub.0 1 .ltoreq. s .ltoreq. N.sub.s find [p.sub.sh, p.sub.ex]
using an iterative water filling algorithm Apply [p.sub.sh,
p.sub.ex] to [Equation 5] and [Equation 6] Find [p.sub.ex.sup.*,
p.sub.sh.sup.*] by substituting [p.sub.sh, p.sub.ex] into [Equation
5] and [Equation 6]
[0088] Herein, m represents the number of cellular terminals, M
represents a total number of cellular terminals, m* represent the
resource block having the highest D2D performance, s represents the
detected D2D group, N.sub.s represents a total number of D2Ds
allocated to the group, p.sub.o represents an initial power, s*
represents an optimal D2D group, p.sub.sh represents the power to
be allocated to the shared resource block, p.sub.ex represents the
power allocated to the exclusive resource block,
.gamma. s = 1 N .sigma. 2 n = 1 N h ex ( s , n ) d 2 d 2 p ex ( s ,
n ) d 2 d ##EQU00020##
represents an average signal-to-noise ratio (SNR) of D2D users
using the exclusive resource block.
[0089] Using the algorithm as described above, the base station 100
may improve spectral efficiency in each D2D communication as well
as in the overall D2D communication by adjusting the powers
allocated to the shared resource block and the exclusive resource
block, while maintaining the total amount of power in the overall
D2D communication system.
[0090] FIG. 4 is a drawing for illustrating spectral efficiency
associated with D2D transmission powers according to the exemplary
embodiment of the present invention.
[0091] FIG. 4 shows experimental results of performance of the D2D
communication system according to the exemplary embodiment of the
present invention and the resource and power allocation method
using the same under a 3GPP LTE-Advanced environment according to
parameters as shown in the following Table 2.
TABLE-US-00002 TABLE 2 Parameter Value Parameter Value Cell radius
(m) 500 D2D transmission distance 50 Total bandwidth 10 No. of Ex
resources 1 No. of sub-channels 48 Thermal noise PSD (dBm/Hz) -174
No. of subcarriers (N) 12 Noise figure (dB) 5 Subcarrier bandwidth
(kHz) 15 Pathloss exponent 4 Maximum Tx power 23 Cellular target
SNR (dB) 20
[0092] FIG. 5 shows spectral efficiency (bps/Hz/cell) of the D2D
system under various conditions of the D2D transmission power
(dBM).
[0093] In FIG. 5, dotted lines ((a), (c), (e)) represent
performance of a D2D system using only the exclusive resource, and
solid lines ((b), (d), (f)) represent performance of a D2D system
using both the exclusive resource and the shared resource according
to the exemplary embodiment of the present invention.
[0094] A dotted line with black circles (a) represents a case where
the exclusive resource is not shared but is used by a single D2D
terminal, a dotted line with black squares (c) represents a case
where the exclusive resource is shared by a pair of D2D terminals,
and a dotted line with black triangles (e) represents a case where
the exclusive resource is shared by four D2D terminals.
[0095] That is, when only the exclusive resource is used, it can be
seen that the spectral efficiency is improved by a frequency reuse
gain when the number of D2D users (N.sub.s) sharing the same
resource increases.
[0096] In addition, a graph of a solid line with blue circles (b)
shows spectral efficiency when a single D2D terminal uses the
exclusive resource and the shared resource, a solid line with red
squares (d) shows spectral efficiency when two D2D terminals
sharing the exclusive resource use the shared resource together,
and a solid line with blue triangles (f) shows spectral efficiency
when four D2D terminals sharing the exclusive resource use the
shared resource together.
[0097] As de, it can be seen that the D2D system proposed in the
present invention shows considerably excellent performance in terms
of spectral efficiency.
[0098] According to the exemplary embodiment of the present
invention, in the D2D system using the cellular resources, the
spectral efficiency of the D2D system can be improved through the
resource allocation for sharing the resources of the cellular users
along with the exclusive resource allocation for the D2D users.
[0099] In addition, in the present invention, the D2D transmission
power is limited to guarantee the performance of the cellular user
when the cellular resource is shared, and the spectrum efficiency
and the performance of the entire cells can be improved by the
plurality of D2D users forming the group to spatially reuse the
same resource.
[0100] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
[0101] Accordingly, the actual technical protection scope of the
present invention must be determined by the spirit of the appended
claims.
* * * * *